For decades the automotive electric starter for internal combustion engines has remained essentially unchanged. It is a low-cost accessory that has performed well under adverse conditions. However, such standard production starters must attain a zero rotational speed prior to reengagement to prevent gear tooth damage. This requires that the starter motor be braked to a stop after disengagement. Should the engine stall after the first crank, a second cranking can be carried out. The braking of the starter motor is normally achieved by use of excessive brush pressure and drag. This results in shortened brush life and has thereby limited the potential life of the standard automotive starter system. Some limitation of life potential is also due to bearing wear caused by tooth vibration accompanying gear tooth interengagement.
An automatic restart system without gear tooth engagement would be most desirable for automotive use because the potential for increased life would be much greater. There have been previous attempts to devise toothless pinion and flywheel starter systems to eliminate gear and noise problems; an early example of this is shown in U.S. Pat. No. 1,817,179. In this patent, the friction means is comprised of a pair of cooperating cylindrical claws which frictionally grip the sides of the flywheel rim. The claws have a friction face, for engaging the flywheel rim, which are disposed substantially in a plane transverse to the start shaft. To move the claws together into a gripping relation, a cam roller is keyed to the armature shaft so as to rotate therewith and force a cam follower on one of the slidable claws to move toward the other claw in response to relative rotation. This apparatus is undesirable because it will have a slow response in cycling for restarting due to the lack of an overrunning clutch and due to the necessity for overcoming a coil compression spring attempting to maintain separation between the claws. Operating deficiences will arise because of the use of coil compression spring which tends to jam up and become wrapped during operation, preventing a smooth and quick release upon overrunning. Due to the use of solely a metal-to-metal interengagement at the friction faces, nonuniform friction will be produced which will not be proportional to the torque of the starting motor. Such device as illustrated in this patent has not been used commercially, principally because it has a low efficiency of operation.
In U.S. Pat. No. 4,092,870, an engine starting mechanism is disclosed which uses two gripping rollers, the control roller of which is forced toward the other roller for gripping of a flywheel as a result of inertial forces. The control roller is caused to be screwed toward the other. This apparatus is deficient because it relies upon screw threads to promote interengagement between the gripping rollers or claws and because it uses rubber inserts for a total rubber-to-metal interengagement, the friction of which cannot be consistently controlled at all times. Due to the abrupt angle between the interengaging faces of the sides of the flywheel and the gripping rollers, additional problems will be encountered in friction control. This device will have a relatively slow response in recycling for restarting due to the absence of an overrunning clutch and the necessity for the flywheel to unscrew the control roller by overcoming the compression spring.